We have a Vietnamese idiom, "như cá nằm trên thớt" - literally, "like a fish on cutting board". My apology for the rough translation because I regard myself as an English learner who is above the average a bit. The meaning of the idiom is: implying a dangerous and almost unescapable situation in which a person's life or fate is in someone's hands and seriously threatened.
I have looked for a similar expression in the idioms section of thefreedictionary and other websites such as merriam-webster and the OED but they appear to have other expressions that are not related to the word "fish".
Is there an English version or a metaphor of the mentioned idiom?
Besides, many presume the Vietnamese idiom to be exactly identical to the Japanese one. However, they do have a slightly different meaning regarding their contexts.